Development and characterization of electrically conductive thermoplastic based composite materials for fuel cell bipolar plates
MetadataShow full item record
Thermoplastic composites exhibit multiple attractive attributes, such as lightweight, low cost, ease and speed of manufacturing, and ability to recycle, which make them ideal for a wide range of applications. Composites containing conductive fillers have lower resistivity and better ability to conduct heat and electricity, which make them potential candidates for fuel cell bipolar plates. The purpose of this study is to develop electrically conductive thermoplastic composites that can be used for the manufacturing of fuel cell bipolar plates. Graphite, Carbon Fiber (CF), Multi-walled Carbon Nanotubes (MWCNT), Carbon Black (CB), and Expanded Graphite (EG) were used as conductive fillers. These fillers were added to three different polymer matrices: Polypropylene (PP), Nylon, and Thermoplastic Polyurethane (TPU). The composites were prepared using the melt-compounding technique in a twin-screw extruder. Thermogravimetric Analyzer (TGA), Differential Scanning Calorimetry (DSC), Digital microscope, and Scanning Electron Microscope (SEM) were used for thermal and morphological characterization. The flexural strength testing of the composites was carried out by using a Dynamic Mechanical Analyzer (DMA). The conductive fillers were added to the polymer in binary, ternary, and quaternary configurations. A full factorial design of L-27 Orthogonal Array (OA) was used as a Design of Experiment (DOE) to evaluate the effect of the filler and the possibility of any interactions between them. The experimental data were interpreted by the Analysis of Variance (ANOVA) to evaluate the significance of each secondary filler. The material formulation with 4 wt.% MWCNT, 5 wt.% CB, 30 wt.% EG, and 25 wt.% PP was the best formulation in terms of material properties, having an electrical conductivity of 124.7 and 39.6 S/cm in in-plane and through-plane directions, and flexural strength of 29.4 MPa. Furthermore, statistical modeling was performed by Response Surface Methodology (RSM) to predict the properties of the, which demonstrated an average accuracy of 83.9% and 93.4% for predicting the values of electrical conductivity and flexural strength, respectively. Also, the bipolar plates were manufactured by sheet extrusion process to examine the processability of electrically conductive thermoplastic composites.